[graph-tool] Normalized betweenness centrality

Hi, I'm a bit confused with the definition of normalized betweenness centrality in the documentation: http://projects.forked.de/graph-tool/wiki/BetweennessCentrality#BetweennessC entrality Basically, I'm looking at Freedman, Sociometry 40 (1), 35-41 and at the boost graph library page: http://www.boost.org/libs/graph/doc/betweenness_centrality.html Both the paper and the boost web pages mention a normalization factor of (n-1)(n-2)/2. However the 1/2 factor seems to be missing from the graph-tool documentation -is this just a documentation typo? Cheers, Rui